Automatically dissolving edges in quad faces that share same normals
A partial solution that lower the mesh vertices but does not keep the quads.


Join the two shapes (to work both on 'Marco' and 'Aries'). For that select them both in object mode, then CtrlJ
Go to edit mode and delete the bottom faces vertices, so that you keep only the top faces


At this step you have the exact same shape, except it is flat :



Go to object mode
Convert to curve AltC, then "curve from mesh/text"


You obtain this (no faces) :




Go to the properties panel and in the curve tab, then click on 2D




This makes the faces reappear :


Now to regive volume. Convert again to mesh (AltC then "Mesh from curve/.../text")

The inner mesh is the following :


You can now extrude it again to regive the original volume.

So no quads. But starting with 41 402 vertices, you now have 8 080. And the shape is the same.